linux-kernel - Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

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Message-ID: <20140910182744.GJ5387@tassilo.jf.intel.com>
Date:	Wed, 10 Sep 2014 11:27:44 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	mingo@...nel.org, eranian@...gle.com, tglx@...utronix.de
Subject: Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

> Note that since then we have actually fixed the 'cannot fault from NMI
> context' thing, so we should be able to actually take those faults. I
> suspect we can simply remove those WARNs from the vmalloc fault path,
> but it would need double checking to see if there's no other reasons.

I think we actually need to use vmalloc_sync_all, because the PEBS/DS
microcode may do the first access, and those lose events when
the page is not present.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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